Apparatus and method for recognizing traffic sign board

Abstract

A method and apparatus for detecting and recognizing a traffic sign using a modified census transform (MCT) feature are disclosed. The traffic sign recognizing method according to an exemplary embodiment of the present invention includes detecting a traffic sign candidate region from an input image using a modified census transform (MCT) feature; verifying whether the candidate region corresponds to a traffic sign using the MCT feature histogram for the candidate region; and lassifying a region of interest into the corresponding traffic sign step by step using the MCT feature histogram for the verified candidate region.

What is claimed is: 
     
       1. A traffic sign recognizing method, comprising:
 detecting a traffic sign candidate region from an input image using a modified census transform (MCT) feature; 
 verifying whether the candidate region corresponds to a traffic sign using the MCT feature histogram for the candidate region; 
 classifying a region of interest into the corresponding traffic sign using the MCT feature histogram for the verified candidate region; and 
 matching the region of interest using a radial symmetry detection (RSD) based on voting in a gradient direction using a deviation of an X axis value and a deviation of a Y axis value of each pixel of the input image. 
 
     
     
       2. The method of  claim 1 , wherein the detecting of a candidate region comprises:
 designating a kernel window having a size with respect to a pixel to be transformed in the input image; and 
 comparing an average of pixel values of pixels included in the kernel window with individual pixel values to calculate n digit bits of MCT feature by assigning a value of 1 to the pixel, in response to the pixel value of the corresponding pixel being larger than the average of the pixel values, and assigning a value of 0 to the pixel, in response to the pixel value of the corresponding pixel being smaller than the average. 
 
     
     
       3. The method of  claim 1 , wherein the detecting of a candidate region comprises:
 extracting the MCT feature for every pixel of the input image using the pixel value of the input image; and 
 classifying the candidate region from the input image using a classifier in which an MCT feature for the traffic sign is trained using at least one of an AdaBoost algorithm or a cascade algorithm. 
 
     
     
       4. The method of  claim 1 , wherein the detecting of the candidate region comprises:
 extracting the MCT feature for every pixel of the input image using the pixel value of the input image; 
 classifying n features from the extracted MCT features using a classifier in which the MCT feature for the traffic sign is trained; and 
 classifying m features, excluding the n features, among remaining MCT features. 
 
     
     
       5. The method of  claim 1 , wherein the verifying comprises:
 creating an MCT feature histogram for an MCT feature value and a frequency of the value using the MCT feature for each pixel of the candidate region; and 
 verifying the MCT feature histogram of the input image using a classifier in which the MCT feature histogram for the traffic sign is trained. 
 
     
     
       6. The method of  claim 1 , further comprising creating an MCT feature histogram for each of a plurality of regions within the region of interest to form a multilevel classification tree in which each level contained therein is used to classify the region of interest according to a type of traffic sign classification. 
     
     
       7. The method of  claim 1 , further comprising creating a first MCT feature histogram in a first region of the region of interest in an N-th level and a second MCT feature histogram in a second region of the region of interest in an N+1-th level. 
     
     
       8. The method of  claim 1 , further comprising:
 classifying the traffic sign as a speed sign, in response to classifying the region of interest as a speed sign region, and classifying the traffic sign as a non-recognized target sign, in response to classifying the region of interest as an other sign region. 
 
     
     
       9. A traffic sign recognizing apparatus, comprising:
 a processor configured to;
 detect a traffic sign candidate region from an input image using a modified census transform (MCT) feature; 
 verify whether the candidate region corresponds to a traffic sign using the MCT feature histogram for the candidate region; 
 classify a region of interest into the corresponding traffic sign using the MCT feature histogram for the verified candidate region; and 
 match the region of interest using a radial symmetry detection (RSD) based on voting in a gradient direction using a deviation of an X axis value and a deviation of a Y axis value of each pixel of the input image. 
 
 
     
     
       10. The apparatus of  claim 9 , wherein the processor is further configured to:
 designate a kernel window having a size with respect to a pixel to be transformed in the input image; and 
 compare an average of pixel values of pixels included in the kernel window with individual pixel values to calculate n digit bits of MCT feature by assigning a value of 1 to the pixel, in response to the pixel value of the corresponding pixel being larger than the average of the pixel values, and assigning a value of 0 to the pixel, in response to the pixel value of the corresponding pixel being smaller than the average. 
 
     
     
       11. The apparatus of  claim 9 , wherein the processor is further configured to:
 extract the MCT feature for every pixel of the input image using the pixel value of the input image; and 
 classify the candidate region from the input image using a classifier in which an MCT feature for the traffic sign is trained using at least one of an AdaBoost algorithm and a cascade algorithm. 
 
     
     
       12. The apparatus of  claim 9 , wherein the processor is further configured to:
 extract the MCT feature for every pixel of the input image using the pixel value of the input image; 
 classify n features from the extracted MCT features using a classifier in which the MCT feature for the traffic sign is trained as a first step; and 
 classify m features, excluding the n features, among remaining MCT features. 
 
     
     
       13. The apparatus of  claim 9 , wherein the processor is further configured to:
 create an MCT feature histogram for an MCT feature value and a frequency of the value using the MCT feature for each pixel of the candidate region; and 
 verify the MCT feature histogram of the input image using a classifier in which the MCT feature histogram for the traffic sign is trained. 
 
     
     
       14. The apparatus of  claim 9 , wherein the processor is further configured to create an MCT feature histogram for each of a plurality of regions within the region of interest to form a multilevel classification tree in which each level contained therein is used to classify the region of interest according to a type of traffic sign classification. 
     
     
       15. The apparatus of  claim 14 , wherein the processor is further configured to create a first MCT feature histogram in a first region of the region of interest in an N-th level and a second MCT feature histogram in a second region of the region of interest in an N+1-th level. 
     
     
       16. The method of  claim 2 , further comprising calculating bits resulting in obtaining a decimal feature vector, based on binary-coded result values for pixels not to be transformed. 
     
     
       17. The method of  claim 1 , further comprising creating a first MCT feature histogram for a first half of the region of interest and a second MCT feature histogram for a second half of the region of interest. 
     
     
       18. The method of  claim 1 , wherein the classifying the region of interest into the corresponding traffic sign is performed step-by-step. 
     
     
       19. The method of  claim 1 , wherein the matching further comprises determining a point having a highest voted value as a center point of a circle. 
     
     
       20. The method of  claim 19 , wherein the matching further comprises matching the region of interest with a rectangular region encompassing a radius of the circle, the radius is obtained in response to the center point of the circle being considered as a center of the region of interest, and the radius is one half of a length corresponding to one edge of the region of interest. 
     
     
       21. A non-transitory computer-readable medium storing instructions that, when executed by one or more processors, cause the one or more processors to perform the method of  claim 1 .